This project will further characterize a potentially novel neuroactive substance, partially purified from bovine and rat brain, which activates the hydrolysis of cellular phosphoinositides in slices of rat cerebral cortex. Phosphoinositide hydrolysis is a receptor transduction event which a number of neurotransmitters utilize. The partially purified material to be studied (PSF, for Phosphoinositide Stimulatory Fraction) is unique in that its actions are not mediated via receptors presently known to be linked to phosphoinositide hydrolysis in brain. Due to the molecular weight range (800-1300 daltons based on gel filtration) and solubility characteristics of this material, it is hypothesized that PSF activity might be due to the extraction of a novel peptide or glycopeptide neurotransmitter or neuromodulator substance. This proposal will determine the regional distribution of PSF material within bovine brain for future purification purposes. The hypothesis that PSF is a peptide or glycopeptide substance will then be tested by examining the effects of specific chemical reactions (e.g. periodate oxidation of carbohydrates) and peptidase enzymes on phosphoinositide stimulatory activity in the partially purified material. Furthermore, experiments will be carried out to study a possible neurotransmitter role for PSF material. Brain slices will be depolarized in vitro to determine if PSF activity can be released from neurons in a calcium-dependent (exocytotic) manner. This project is intended to provide the basis for future studies which will fully characterize and purify the active substance in the PSF material.